In this lesson basic chemistry concepts from grade ten science and grade eleven chemistry were reviewed, such as bonds, polarity, and intermolecular forces.
Intramolecular Forces
- atoms bond in order to have the same number of electrons in their outer valence shell as the closest noble gas.
- ionic bonds form between a metal and a non metal
the metal gives electrons to the non-metal
the metal becomes a positively charged cation, the non-metal a negatively charged anion
- covalent bonds form between two non metals
the electrons are not transferred as in an ionic bond - they are shared
a pure covalent bond occurs when the sharing is completely equal and the two atoms have the same electronegativity value (such as two C atoms)
a polar covalent bond occurs when there is an unequal sharing of the electrons and the atoms have a different electronegativity value
in a polar covalent bond the atom with the higher electronegativity has a slight negative charge and the atom with the lower electronegativity has a slight positive charge.
Polar Molecules
- a molecule that contains polar bonds may or may not be overall polar
- in a polar molecule charges are unevenly distributed - polar bonds and asymmetry in the molecule must be present
- if the molecule is symmetrical, the charges are cancelled out and the molecule is overall non polar.
Intermolecular Forces
- are the forces of attraction between molecules
- weaker than intramolecular forces
- physical changes break or weaken these forces
- physical properties of a substance are determined by intermolecular forces
- London Dispersion Forces are based on the simultaneous attraction of the electrons of one molecule and the positive nuclei of neighbouring molecules
exist in ALL molecules
strength is related to the number of electrons and protons in each molecule
- Dipole-dipole forces occur between polar molecules and are based on the simultaneous attraction of the positive end of one molecule to the negative end of another
- Hydrogen Bonds are a special type of dipole dipole force that occur between molecules with hydrogen bonded to nitrogen (N), oxygen (O) or fluorine (F)
Are extremely strong due to the immense electronegativity difference between H and the most electronegative elements
For a substance to be able to dissolve in water, it must have the ability to hydrogen bond.
Here is a video that talks about molecular polarity in depth. MAKE SURE YOU WATCH IT WITH THE ANNOTATIONS ON!
A Crash Course in Chemistry
Lesson Date: Monday September 9, 2013
By: Anne Clayton
In this lesson basic chemistry concepts from grade ten science and grade eleven chemistry were reviewed, such as bonds, polarity, and intermolecular forces.
Intramolecular Forces
- atoms bond in order to have the same number of electrons in their outer valence shell as the closest noble gas.- ionic bonds form between a metal and a non metal
- the metal gives electrons to the non-metal
- the metal becomes a positively charged cation, the non-metal a negatively charged anion
- covalent bonds form between two non metalsPolar Molecules
- a molecule that contains polar bonds may or may not be overall polar- in a polar molecule charges are unevenly distributed - polar bonds and asymmetry in the molecule must be present
- if the molecule is symmetrical, the charges are cancelled out and the molecule is overall non polar.
Intermolecular Forces
- are the forces of attraction between molecules- weaker than intramolecular forces
- physical changes break or weaken these forces
- physical properties of a substance are determined by intermolecular forces
- London Dispersion Forces are based on the simultaneous attraction of the electrons of one molecule and the positive nuclei of neighbouring molecules
- exist in ALL molecules
- strength is related to the number of electrons and protons in each molecule
- Dipole-dipole forces occur between polar molecules and are based on the simultaneous attraction of the positive end of one molecule to the negative end of another- Hydrogen Bonds are a special type of dipole dipole force that occur between molecules with hydrogen bonded to nitrogen (N), oxygen (O) or fluorine (F)
Here is a video that talks about molecular polarity in depth. MAKE SURE YOU WATCH IT WITH THE ANNOTATIONS ON!